Information transmission method for a wireless local network

ABSTRACT

Method for data transmission in a wireless local area network refers to wireless local area networks (WLAN) consisting of a multitude of transceivers capable of establishing communication with one another (i.e. operating in a peer-to-peer mode). Implies the determination of the quality of communication between all transceivers and storage of communication quality data by each of the transceivers. Based on stored data on communication quality, a transceiver operating in the transmission mode transmits information to an addressee by a transmission route that provides for the quality of communication, which is equal to or better than a specified threshold value of communication quality. Stored data are updated periodically. The method improves the quality and reliability of communication for WLAN users (including mobile users) thus increasing the data transmission rate.

FIELD OF THE INVENTION

The invention claimed herein refers to wireless local communicationnetworks (WLAN) that include multiple users capable of establishingcommunication with one another (i.e. operating in a peer-to-peer mode),in particular, to methods for transmitting various types of informationused in such networks.

BACKGROUND ART

At present wireless local area networks are gaining wide recognition inthe field of information science and video graphic communication for thepurpose of transmitting and distributing data among multiple userslocated in one building (for example, among PCs, laptops, PDAs, printersand other users) without limiting the “mobility” of said users.Transmission of information with the use of WLANs reduces the cost ofnetwork because there is no need for laying connecting wires. A networkof this type can be also used in cases when it is difficult or simplyimpossible to lay connecting wires and in cases when there are no socketconnectors for local networks due to architectural limitations. WLAN isan ideal solution for companies and institutions in which users areoften rearranged within premises. As a rule, existing WLANs are builtbased on the principle of equal rights of all network users, and radiocommunication in existing WLANs is arranged according to well-knowninternational standards—e.g. standards IEEE 802.11, IEEE 802.11a, IEEE802.11b and ISO 8802-11, HIPERLAN of type 2.

The distinguishing feature of WLAN consists in the fact thatcommunication quality (and, hence, data transmission rate between twousers) depends heavily upon a number of factors and in addition,communication quality is not constant in time. For example, thestandards indicated above provide that four data transmission rates—11,5.5, 2 and 1 Mbps—are to be used depending on communication quality.According to these standards, the rate of data transmission is to be setstage by stage, at first transmission is performed at a rate of 11 Mbps,and with poor quality of communication the rate of data transmission isdecreased step-by-step. When the quality of communication between twousers is very poor, data exchange is carried out at a rate of 1-2 M bps.Such a switchover from one data transmission rate to another one resultsin the increase in time of information transmission from one user toanother.

Methods are known in which communication is arranged in a wireless localnetwork between users, which are unable to transmit information directlyto one another (See U.S. Pat. No. 4,987,536; EP Patent Nos. 0,481,171and 1,117,270; Russian Patent No. 2,037,961 and PCT Patent ApplicationNos. PCT/SE00/00633 and PCT/US00/41180).

For example, in a known method for data transmission in a wirelesscomputer network (See PCT Patent Application No. PCT/US00/41180) each ofthe users determines one or more “labeled routing trees”—i.e. shortestpaths for communication links with other users. Then each user sends“labeled routing trees” (built by him) to other users who store them andthen form the common “labeled routing tree” of the shortest path fordata exchange with other network users based on stored individual“labeled routing trees”.

The known method, while providing for the transmission of messages toaddressees by the shortest pathway, doesn't take into account the factthat in some sections of the selected route, the quality ofcommunication may be not good enough, and, hence the rate of datatransmission to users would be low.

It has to be pointed out here that when the quality of communicationbetween a pair of users in WLANs built in accordance with the principleof equal rights for all network users is poor, there is often a thirduser, the quality of communication of which with both users from thesaid pair of users is good and who is capable of exchanging data withboth of them at a rate of 5.5 or 11 Mbps.

It terms of the set of the most essential features, the closest analogto the invention claimed herein is the method for radio communication ina wireless local area network (See U.S. Pat. No. 6,115,580) thatincludes the determination of the quality of user-to-user links, withsaid quality being determined based on calculations of terraininformation and location of users, storage of said calculated data onthe quality of user-to-user links between all users and transmission ofinformation to an addressee (out of the number of users located oninformation transmission route) who is characterized by goodcommunication quality (calculated at the first stage).

The known method for selecting a route for transmitting information toan addressee based on calculated data on his current location doesn'tallow one to take into account actual conditions of communicationbetween users (presence of moving obstacles within WLAN operation area,radio interference/noise and the like).

SUMMARY OF THE INVENTION

The purpose of the present invention consists in creating such a methodfor data transmission in a wireless local area network, which would makeit possible to improve the quality and reliability of communication fornetwork users (including mobile network users), thus raising the datatransfer rate.

The invention is based on the recognition that in a WLAN, which includesa plurality of transceivers in spaced-apart locations, a transmissionfrom one of the transceivers to a selected receiver destination can beoptimized by sending the transmission along optimum quality pathsegments from transceiver to transceiver. The optimum path segments aredetermined conveniently by comparing consecutive entries in a linkquality table. Each transceiver may include a direction-agile antenna,which is oriented in the direction to optimize transmission andreception of each received data packet.

This advantage is achieved due to the fact that following steps arecarried out in a method for radio communication in a wireless localnetwork consisting of a multitude of transceivers capable ofcommunicating in a peer-to-peer mode:

-   -   Determination of the quality of communication between all        transceivers of WLAN,    -   Storage by each network transceiver of received data on quality        of communication between all pairs of transceivers of the        network,    -   Transmission of information by a transceiver operating in the        transmission mode to an addressee out of the number of this        network transceivers along the information transmission route        that provides for the quality of communication that is equal to        or better than a specified threshold value of communication        quality. Said transmission is performed using at least one        intermediate transceiver out of the number of this network        transceivers as a retransmitter.

In the particular case, determination of said quality of communicationbetween all transceivers of WLAN may be conducted in the followingmanner:

-   -   Each transceiver of this network transmits an identification        signal that includes data on quality of communication with other        transceivers of this network,    -   Each transceiver of this network receives an identification        signal from other transceivers of this network.

To increase the communication range, reception of identification signalcan be performed when the antenna beam is positioned in the direction oftransceiver operating in the transmission mode.

It is desirable to take data on the quality of communication in thepeer-to-peer operation mode with said addressee as a specified thresholdvalue.

The quality of communication can be determined based on the level ofreceived signal or on the signal-to-noise ratio.

Transmission of information by transceivers to addressees by a selectedroute can be conducted at a rate determined using the stored data on thequality of communication between them

Stored data on the quality of communication can be taken as the currentvalues for the purpose of subsequent transmission of information to saidaddressee.

Since conditions of radio communication between transceivers in WLAN mayvary in time, it is desirable to repeat the cycle of said determinationof the quality of communication and the storage of said data oncommunication quality periodically. These cycles can be repeated at atime interval from 0.1 s to 100 s.

Following the repetition of the cycle of said determination of thequality of communication between WLAN transceivers, data stored in theprevious cycle are replaced with data on communication quality obtainedin the current cycle and then the storage of the newly obtained data isarranged. Effective monitoring of changes in WLAN radio space may beconducted in the following manner. Data on communication quality storedafter a previous said cycle are compared with data on communicationquality stored after the next cycle and when data values of both cyclesare the same, the time interval between cycles of communication qualitydetermination is either kept the same as it was or increased. When dataon communication quality stored after a previous cycle are differentfrom data obtained and stored after the next cycle, the interval betweencycles is decreased.

In that way, the invention claimed herein significantly improves theaverage data transfer rate in a WLAN providing either direct datatransfer between users or engaging intermediate stations in the WLAN asretransmitters, depending on the link quality of all availablecommunication routes between these users.

A wireless local area network (for which the method claimed herein isintended), includes a plurality of spaced-apart transceivers, with eachof the transceivers including first means for transmitting separately anidentification code including data on the quality of communication inthe transmission path between it and each other of the plurality oftransceivers; second means for receiving the identification code foreach of the other transceivers in plurality of the transceivers and forreal time determination from the above-mentioned data of each quality ofcommunication for the best path available and third means responsive tothe receipt of the identification codes for other transceivers forstoring data representative of the quality of communication between eachpairs of the transceivers of said network.

Each of the transceivers normally is operating in the receiving mode andeach of the transceivers includes user responsive means for switching tothe transmitting mode.

The transceiver operating in the transmitting mode includes means fortransmitting to a selected addressee receiving transceiver, which meansprovides for a quality of transmission at least equal to a specifiedthreshold.

The intermediate transceiver is selected using the stored data on thequality of communication between all pairs of said plurality oftransceivers in such a way, as it is located on the highest qualitycommunication route between the transmitting transceiver and theaddressee transceiver.

A communication path is constructed in real time mode using a sequenceof the transceivers in a relay from an initiating transmittingtransceiver to an intended recipient transceiver.

Each of said transceiver may further include control means responsive tothe receipt of a transmission for terminating the transmission of theidentification code.

Each of said plurality of transceivers may further include a directionagile antenna means responsive to the transmission for orienting theantenna in the direction in which transmission is received.

The means for storing includes a link quality table. It may also includemeans for periodically updating said link quality table with theupdating period being either pre-specified in advance or a function offrequency of changes in the quality of communication.

Each of the transceivers may further include means for comparing qualitydata for each of consecutive transmission of identification codetransmissions and for controlling the interval between consecutiveidentification code transmissions.

Each transceiver may further include means for receiving andre-transmitting data packets not addressed thereto, and each of thetransceiver also can include means for selecting a highest quality pathsegment to an intermediate other transceiver in said network forrelaying said packet to the receiver to which the packet is directed.

Each of the transceivers also includes means for determining a highestquality transmission path between itself and different othertransceivers in said network.

A wireless local area network may include a plurality of transceivers inspaced-apart location, with each of these transceivers including meansresponsive to receipt of a data packet intended for a differenttransceiver for re-transmitting data packet along a highest qualitytransmission path.

A transceiver for a wireless local area network includes means fordetermining in successive periods the quality of communication of thetransmission paths between said transceiver and each of othertransceivers in said network and for storing data represented of saidquality for successive ones of said periods.

A transceiver may also include means for comparing quality oftransmission path data in successive consecutive ones of the periods forvarying the intervals between the periods.

Each of the transceivers (which normally is in the receiving mode) mayfurther include user responsive means for switching from the receivingmode to the transmission mode for transmitting a data packet and meansresponsive to the reception of a data packet being transmitted to adifferent receiver for re-transmitting said data packet along a highestquality communication path. It may also include means for determiningsaid highest quality communication path from said stored datarepresentative of said quality.

The transceiver may also include means responsive to the receipt of adata packet for terminating the transmission of said identificationcodes.

The transceiver may further include a direction agile antenna and meansresponsive to the receipt of a data packet for re-orienting the antennain the direction from which the data packet was received.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments, features and advances of the present inventionwill be understood more completely hereinafter as a result of a detaileddescription thereof in which reference will be made to the followingdrawings:

FIG. 1—schematically illustrates the operation of transceivers inexisting WLANs;

FIG. 2—presents an example of radio communication session in a WLAN inaccordance with the present invention;

FIG. 3—presents an example of a Table of stored data on communicationquality (s/n—is the designation used for signal-to-noise ratio);

FIG. 4—schematically illustrates the sequence of steps carried out by aWLAN transceiver in the course of data transmission;

FIG. 5—schematically shows a WLAN transceiver used in the datatransmission method claimed herein.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Transceiver 1 (FIG. 5), which is used for the implementation of the datatransmission method in WLAN claimed herein includes a receiver 2, memoryblock 3, controller 4, transmitter 5 and reception/transmission switch6, to which antenna 7 is connected. A wireless local network (for whichthe method claimed herein is intended—see FIG. 1) includes a multitudeof users 8, 9, 10, . . . N, each of which is equipped with transceiver1. Users 8, 9, 10, . . . N are capable of direct communication with oneanother (i.e. capable of operating in the peer-to-peer mode), but thequality of communication between some of these users is not good enough.For example, due to radio interference (mentioned above) the quality ofcommunication between users 8 and 9 is so that data exchange betweenthem can be carried out only at a rate of 2 Mbps, while the quality ofcommunication between users 9 and 10 is so that data exchange betweenthem can be carried out at a rate of no greater than 1 Mbps (FIG. 1).

In accordance with the method for data transmission in WLAN claimedherein, first the quality of communication between all users 8, 9, 10, .. . N is determined. Determination of the communication quality may beperformed, for example, in the following manner. Each of thetransceivers 1 of users 8, 9, 10 . . . N transmits an identificationsignal that includes data on the quality of communication with othertransceivers of WLAN and receives from other devices the sameidentification signals. To increase the reception range, reception ofidentification signals by transceivers may be performed when theirantenna beams are positioned in the direction of the transceiver devicethat is in the transmission mode. Each of the transceivers 1 of users 8,9, 10, . . . N retrieves data on the quality of communication fromreceived identification signals and stores these data as current valuesfor the purpose of subsequent transmission of information to a specificaddressee in the network. Storage of communication quality data by eachof the transceivers 1 of users 8, 9, 10, . . . N may be carried out, forexample, in a communication quality Table (called the Link QualityTable)—that is arranged in the form of a two-dimensional arraycontaining information on the quality of communication between all pairsof transceivers 1 out of the set of users 8, 9, 10, . . . N (FIG. 3).The quality of communication can be determined for example based on thelevel of a signal being received or on the signal-to-noise ratio. TheLink Quality Table can be updated periodically to maintain the adequatereliability of information contained in it. Updated data for the Tableare obtained as a result of periodical repetitions of the cycleconsisting in the transmission of identification signals by each of theWLAN transceivers 1 of users 8, 9, 10 . . . N to all other transceiversin WLAN, in the reception of corresponding identification signals fromeach of the WLAN transceivers 1 of users 8, 9, 10, . . . N and storageof received data on communication quality. The update period for theLink Quality Table may be either specified in advance (for example, at aspecified time interval from 0.1 s to 100 s) or it can be changeddynamically according to the frequency of changes in the quality ofcommunication between WLAN transceivers 1 of users 8, 9, 10, . . . N.For this purpose each of the transceivers 1 of users 8, 9, 10, . . . Ncompares communication quality data stored after a previous cycle withthose obtained as a result of the next cycle. If data on communicationquality stored after a previous cycle and data on communication qualitystored after the next cycle are the same, the interval between saidcycles is kept the same as it was or increased. If data on communicationquality obtained as a result of the last cycle differ from those storedafter a previous cycle, the time interval between cycles is decreased.Data on communication quality, put down in the Link Quality Table aftera previous cycle are then replaced with data on communication qualityobtained as a result of the last cycle conducted to be used as currentvalues. Besides the method described above, storage and processing ofdata on communication quality can be carried out by any other knownmethod. Transmission of information by a transceiver operating in thetransmission mode to an addressee out of the number of WLAN transceivers(via intermediary transceivers) is made by a transmission route thatprovides for the quality of communication that is equal to or betterthan a specified threshold value of communication quality which isselected using the stored current values of data on communicationquality. Transmission of information to an intermediary is conducted ata rate determined based on stored data on the quality of communicationwith this specific intermediary. Usually the quality of directconnection with an addressee (peer-to-peer connection) is taken as saidthreshold value.

TECHNICAL APPLICABILITY

Using the method described above the authors have conducted thetransmission of information to addressees in WLAN in accordance withIEEE standards 802.11b and ISO 8802-11 (FIG. 2, FIG. 3). Data aretransmitted in packets in such WLANs. Upon the reception from a user 9of data packet to be re-transmitted to user 10 and prior tore-transmitting this packet to the addressee, transceiver 1 checks thequality of communication with this addressee using the Link QualityTable for this purpose. Since the quality of communication with theaddressee is poor in our case (data transmission at a rate of 2 Mbps),transceiver 1 looks for an intermediary in the Link Quality Tablecapable of transmitting said data packet to user 10 at a higher rate andfinds such an intermediary-transceiver 1 of user N. In this casetransceiver 1 of user 9 adds service information about the addressee tothe said data packet and sends the latter via transceiver 1 of user N tothe addressee (i.e. transceiver 1 of user 10). In another case—forexample, when it is needed to transmit data from transceiver 1 of user 8to transceiver 1 of user N—the quality of communication between them isquite good (which fact is determined based on the Link Quality Table)—11Mbps. Hence, transceiver 1 of user 8 sends this data packet directly totransceiver 1 of user N (no intermediary is involved in this case).

The example given above does not limit other possible options for theimplementation of the method for data transmission in existing WLANsclaimed herein.

REFERENCES CITED

-   1. U.S. Pat. No. 4,987,536, Int. Cl. G06 F 13/38, publ. 22 Jan.    1991.-   2. EP Pat. No. 0 481 171, Int. Cl. H04L 12/66, publ. 22 Apr. 1992.-   3. RU Pat No. 2 037 961, Int. Cl. H04B 7/00, publ. 19 Jun. 1995.-   4. PCT/SE00/00633, Publication No. WO 00/60816, Int. Cl. H04L 12/56,    publ. 12 Oct. 2000.-   5. PCT/US00/41180, Publication No. WO 01/30035, Int. Cl. H04L 12/56,    publ. 26 Apr. 2001.-   6. EP. Pat. No. 1 117 270, Int. Cl. H04Q 7/38, publ. 18 Jul. 2001.-   7. US. Pat. No. 6 115 580, Int. Cl. H04K 3/00, publ. 05 Sep. 2000.

1. A method for transmitting information in a wireless local areanetwork consisting of a multitude of transceiving devices capable ofoperating in a peer-to-peer mode wherein said method implies thefollowing: (a) Determination of the quality of communication between alltransceiving devices of said network, b) Storage by each of saidtransceiving devices of said network of received data about the qualityof communication between all transceiving devices of said network, (c)Transmission of information by a transceiving device of said networkthat is in transmission mode to an addressee from among transceivingdevices of said network by a route that ensures such quality ofcommunication that either exceeds or equal to a specified thresholdvalue.
 2. The method of claim 1 wherein the determination of saidquality of communication between all transceiving devices of saidnetwork implies the following: (a) Transmission by each transceivingdevice of said network of identification signal that includes data onquality of communication with other transceiving devices of saidnetwork, (b) Reception by each transceiving device of said network ofsaid identification signal from other transceiving devices of saidnetwork.
 3. The method of claim 2 wherein the reception of saididentification signal is performed when antenna beam is oriented in thedirection of said transceiving device that is in transmission mode. 4.The method of claim 1 wherein the quality of communication in thepeer-to-peer operation mode with said addressee is taken as a specifiedthreshold value.
 5. The method of claim 1 wherein the quality ofcommunication is determined based on the level of a signal beingreceived.
 6. The method of claim 1 wherein the quality of communicationis determined based on the ratio of a received signal level to noiselevel.
 7. The method of claim 1 wherein transceiving devices belongingto said information transmission route transmit information (intendedfor an addressee) to one another at a rate determined based on data onquality of communication between them.
 8. The method of claim 1 whereinsaid stored data on the quality of communication are taken as currentvalues for subsequent transmission of information to said addressee. 9.The method of claim 1 wherein the cycle of said determination of thequality of communication and storage of said data on communicationquality is repeated periodically.
 10. The method of claim 9 wherein thecycle of said determination of the quality of communication and storageof said data on communication quality is repeated at a time intervalfrom 0.1 s to 100 s.
 11. The method of claim 9 wherein said data oncommunication quality stored after a previous said cycle are replacedwith said data on communication quality stored after the said nextcycle.
 12. The method of claim 9 wherein said data on communicationquality stored after a previous said cycle are compared with said dataon communication quality stored after the said next cycle and when thedifference between data values of both cycles doesn't exceed specifiedvalue, the interval between said cycles is kept the same as it was orincreased; when the difference between data values of both cyclesexceeds specified value, the interval between cycles is decreased.